Interface conditions and code-switching: Pronouns, lexical DPs, and checking theory

The ban on code-switching between a (subject) pronoun and a verb, but not between a lexical DP and a verb, is an enduring puzzle in research on bilingual code-switching. In this paper, we propose an account of these code-switching facts by positing that pronouns and lexical DPs take advantage of different checking strategies: While lexical DPs check features in [Spec, TP], pronouns undergo D-to-T movement. In the latter case, a mixed-language complex head results, a construction which crashes at PF, as predicted by the PF Disjunction Theorem.